Patent GB-190517370-A (GB)
Title: An Improved Furnace for Roasting, Desulphurising, Chloridising, Dehydrating, or Drying Ores, and other Substances.
Inventor: LEGGO ARTHUR VICTOR
Filed: 1905-08-28
Granted: 1906-05-10
Abstract: 17,370. Leggo, A. V. Aug. 28. Furnaces.-A muffled or unmuffled furnace for roasting, desulphurizing, chloridizing, de-hydrating, or drying ores consists of a series of superimposed hearths having, preferably, separate fire-places, and provided with feeding and discharging devices, and with rabbles fitted to vertical shafts or to shafts of adjustable inclination. The ore is cooled, after roasting, in a separate chamber by means of air, which is afterwards led to the combustion chambers. Where a considerable increase of temperature is required for treating the ore, a direct-fired finishing-hearth is provided. The ore is fed to the hearths 2, 3, 4, 5, Fig. 1, from a hopper 43, Fig. 7, by means of fluted rollers 44, inclined shoots 45, and screw conveyers 47. It is then conveyed along the hearths by the solid rabble arms 18, 17, Fig. 1, the arms 16, cooled by air from a pipe 39, and the arms 15, cooled by water from a pipe 19. At the ends of the hearths, the ore is discharged over projections 63, Fig. 8, and through a hole 64 on an adjustable slide 62 into shoots 48, having hinged shutters 50, 51, and a shoot 49 having a slide, 52. The cam 53, operating the shutter 50, is so arranged that the shutter is opened before the rabble arm 15 reaches the shoot 48, and closed when the ore has passed into the shoot 49. Between the closing of the shutter 50 and the opening of the shutter 51, the slide 52 is opened and closed by the crank 57, so that air is prevented from passing upwards through the shaft 49. In an alternative arrangement for discharging the ore, disks 138, Fig. 10, are fixed to a rotating shaft 139, and the ore passes through holes 142 in the disks into the shoots 48, and leaves the shoot 49 through holes 143 in a rotating disk 140. From the shoot 49, the ore is delivered to a cooling- chamber, or, when a " sweet" roast is required and a considerable increase of temperature is necessary, the ore is first delivered to a finishing-chamber constructed as an extension of the bottom hearth of the furnace. The cooling-chamber 61, Fig. 3, is divided into two parts by a wall 81, and the air used for cooling the ore in the part 72 passes by the flue 73 to the combustion or roasting chambers. By means of the rabble arms 90, the ore is conveyed along the hearths in the part 72 and passes through a hole 88 in a slide 84 and underneath the bottom of the slide 85, and forms a seal in the space between the two slides, thereby preventing air admitted by the inlet 92 from passing to the part 72. The rabble arm 91 passes beneath the slide 85 and at each revolution removes an amount of ore from between the slides, and finally discharges the ore through a shoot 94. The products of combustion from the furnace pass through dampered passages 98, Fig. 1, to a dust chamber 67, Fig. 2. Air, for supply to the furnace, enters a flue 65 and a hollow wall having horizontal baffles, and is then led to the cooling- chamber, whence it passes either directly to the roasting-hearths or to the fire-places through the upcast 74, Fig. 1, and through dampered passages 75 or 77, to produce a reducing or an oxidizing flame, respectively. Arrangements are also described for admitting air heated in the finishing. chamber when no cooling-chamber is used. Cold air may be admitted to the combustion chambers through adjustable ash-pit doors, and to the roasting-chambers through observation openings 101. The hearths may be formed with a depression in the centre to provide for expansion, and may be formed with shallow steps to prevent ore from returning towards the feeding end. A modified arrangement of fire-boxes, which may be used at any point along the length of the furnace as well as at the ends, is shown in Fig. 9. For this arrangement, the upcast 74 and passages 75, 77 have to be modified, and holes 134 are provided for the escape of ashes from, and the ingress of air to, the fire-boxes. When the furnace is constructed with shallow roasting-chambers, transverse arches are formed above the port-holes 101, Fig. 1, so as to permit free access to the rabbles. Salt or carbon is introduced to the roasting- chambers when required through shoots in the side walls. Excess of gas may be removed through flues passing from the side of the furnace to the main flue 66, Fig. 2, or through flues built in the arches leading to the main flue. To convey the ore quickly along horizontal or slightlyinclined hearths, the rabble arms are arranged, as shown in Fig. 16, to rotate obliquely to the hearths. The inclination of the rabble shafts may be adjusted by fitting them in elongated slots 168, Fig. 17, the collars 170 around the shafts being fixed in the desired position by filling the unoccupied part of the opening 168 with masonry or other filling. When the roasting - hearths are muffled, the gases pass through flues 155, Fig. 19, which are built in the hearths or arches and may be provided with baffling-walls 158. A finishing- hearth may be formed by extending the bottom hearths 5, and the lowest fire-box of the previous type is then removed and employed for directly heating the ore on the finishing-hearth when a " sweet " roast is required. In this arrangement, the ore from the hearths 2, 3, 4 is discharged on to the hearth 5 or rabbled over an adjustable slide to the finishing-hearth. The gases of combustion from the latter are led to the two bottom flues 155, and where these gases are sufficient to heat the whole of the muffied chambers, they may be led to au upcast similar to that shown in Fig. 1. The gases generated in the chambers are withdrawn through outlets 165 and used for the manufacture of sulphuric acid &c. If the hearths 2, 3, 4, 5 are worked unmuffled in conjunction with the finishing-hearth, the combustion products from the latter are prevented from diluting the gases of calcination by an ore seal.